Electromagnetically actuating relays in coordinate switches



R, NlTSCH 3,053,938

ELECTROMAGNETICALLY ACTUATING RELAYS IN COORDINATE SWITCHES Sept. 11, 1962 3 Sheets-Sheet 1 Filed March 21, 1956 Fig.2

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ELECTROIVAGNETICALLY ACTUATING RELAYS IN COORDINATE SWITCHES Filed March 21, 1956 3 Sheets-Sheet 2 Fig.5

Sept. 11, 1962 R NITSCH 3,053,938

ELECTROMAGNETICALLY ACTUATING RELAYS IN COORDINATE SWITCHES Filed March 21, 1956. 3 Sheets-Sheet 3 Patented Sept. 11, 1962 3,0539% ELECTROMAGNETECALLY ACTUATKNG RELAYS IN CUGRDHNATE SWITCHES Rudolf Nitsch, Munich dalln, Germany, assignor to Siemens 8: Halslre Alstiengesellschat't, Berlin and Munich,

Germany, a German corporation Filed Mar. 21, 1956, Ser. No. 573,039 Claims priority, application Germany Apr. 5, 1955 4 Claims. (Cl. 179-2754) This invention is concerned with an electromagnetically operating switching device disposed at crossing points of coordinate switches.

A bank of a crossbar or coordinate switch serves the purpose of selectively establishing connections between its crossing rows and columns, the rows representing inlets and the columns representing the outlets of the switch. The crossing points which are to be connected are represented by switching contacts.

A prior switching device for a coordinate switch such as disclosed and claimed in U.S. patent to Ellwood et al., 2,187,115, granted January 16, 1940 comprises row coils and column coils respectively embracing entire rows and columns. At the crossing points of these column and row coils are disposed the switch contacts which are constructed so that the contact springs thereof are actuated by magnetic flux. The contacts are disposed relative to the corresponding line and row coils so that the respective coils embrace the magnetic circuit of the corresponding contact.

The invention constitutes an improvement on the aboveindicated arrangement in Ellwood et al. 2,187,115. The various objects and features of the invention will appear from the description which is set forth below with reference to the accompanying diagrammatic drawings.

Referring to the drawings:

FIG. 1 shows in schematic representation the basic features of a known arrangement such as disclosed and claimed in Ellwood et al. 2,187,115;

FIG. 2 indicates schematically the structure of a contact device used in the known arrangement of FIG. 1;

FIG. 3 illustrates a contact or switching device according to my invention;

FIG. 4 shows the basic features of a coordinate switch employing features of the invention; and

FIG. 5 illustrates a variant of FIG. 4 employing strips of magnetically conductive material for interconnecting the contact elements.

The prior switching device as shown in part in FIG. 1 comprises four crossing points having two row coils A and B and two column coils C and D. At the crossing points there are provided contacts 1, 2, 3 and 4.

One of these contacts is shown separately in FIG. 2. The contact springs are made of magnetizable material and carry the magnetic flux produced for the actuation thereof. The two contact springs face one another at their overlapping ends. The overlapping point forms a working gap which is closed upon actuation of the springs responsive to impressing thereon a magnetic flux to produce across the working gap a magnetic field which draws the springs together. The springs are disposed within a sealed glass tube, the spring terminals extending from such tube to the outside.

A contact structure of this type, as schematically indicated in FIG. 1, for example at 1, is actuated by current flow through the row coil A and through the column coil C. Assuming 100% energization of the coils, there will result for the corresponding contact a 200% energization which must assure reliable actuation. However, if the practically unavoidable tolerances are considered which result from voltage fluctuations, losses due to coil resistance and contact characteristics, and assuming a i20% tolerance which is usually considered permissible, there will result in the most unfavorable case a minimum excitation amounting to 160% which must suflice for effecting contact actuation. As compared with this total excitation, there may be on one side a maximum excitation of (through one coil) at which the contact must not be actuated. These values would appear to be sufiicient for normal contact operation, but they do not sufiice for quick contact actuation which requires an excitation considerably stronger than one that is just about sufiicient for normal operation. The possibility of quick contact actuation is however one of the most important considerations in connection with switches of the indicated kind.

Quick contact actuation by means of strong excitation is however impossible in such a switch because it would require at least two to threefold the magnitude of the excitation, which would result with partial energization through one coil in the actuation of all contacts embraced by such coil; for, if it is assumed that operative excitation is present at 160% total excitation and if the contacts would for quicker actuation be operated at twice such value, namely, with 320%, there would result the operative excitation of 160% for each coil which would cause operative actuation of all contacts associated with such coil.

The indicated arrangement presents a further difiiculty. In order to operate economically, the bank of the coordinate switch is plurally utilized, that is, contacts of the bank are simultaneously closed although they generally do not belong to the identical rows or lines. In such a case an actuated contact must be held operated by special means. In the aforesaid arrangement, this is effected by disconnecting one of the coils and reducing the excitation of the other coil by 50%. It shall be assumed, for example, that contact 1 is closed and held by 50% excitation of the coil C, and that contact 4 is now to be closed by energization of the row coil B and the column coil D. The contact 3 thereby receives a 100% excitation through the row coil B and 50% excitation through the coil C. This total of excitation affecting the contact 3 must however be insufficient for causing operative actuation of such contact. Assuming accurately maintained excitation values and entirely uniform contact structures, it would seem possible to prevent actuation of the contact 3 under these conditions. However, if the tolerance of :20% which is in practice unavoidable is taken into account, there will result an entirely different situation.

The theoretically accurate excitation through two coils each at 100% will result in 200% excitation, while a twofold excitation each reduced by 20% will result in a total excitation of only 80%+80%=160%. This excitation should sufiice for the operative actuation of any desired contact but it comes very close to the above explained excitation of 150% for the contact 3 at which such contact must not operate.

If the excitation of the coils B and C are within the permissible tolerances at their maximum values, namely 120% and 60%, the total excitation will be 180%, and according to the theoretical operating assumption, such excitation should not cause actuation of the contact 3. This requirement cannot be satisfied at all because, as explained above, a contact would be causedto operate already at an excitation of The indicated arrangement is accordingly subject to strongly limiting tolerance requirements which, if at all, could in practice be satisfied only with great difiiculty.

The uncertainty of operation of the above-described known arrangement is further increased by stray magnetic fields radiating from two coils excited at a crossing point, such fields aiiecting neighboring contacts in a premagnetizing sense. In order to divert these stray fields produced by the coils, each coil group comprising row coils and the column coils is in the previously noted Ellwood et al.

patent disposed within a shielding cage made of magnetizable material, the cage embracing the corresponding coil group very tightly. This expedient may reduce the premagnetization of neighboring contacts by stray fields radiating from the coils, but cannot eliminate the aboveexplained difficulties resulting from the tolerances.

The object of the invention is to eliminate the abovedescribed difiiculties. The arrangement according to my invention is such that excitation along one side of a contact cannot result in its actuation. This is achieved according to my invention by providing at each crossing point magnetic shunts between the movable part of the contact springs and the fixed terminal ends thereof, each shunt containing an iron path and an air gap, the air gap lying between the iron path and the movable part of the contact spring, and the flux direction in the air gap extending substantially in parallel to the direction of motion of the contact spring. An example of such a structure is shown in FIG. 3.

Referring now to FIG. 3, a contact arrangement having springs F1 and F2 is disposed sealed within a glass tube G, the contact springs overlapping at U and the spring terminals extending from the tube G. The coils for actuating the contacts are disposed one on each side of the overlap U; it shall be assumed that these coils are respectively a row coil A and a column coil C. Next to the row coil A is disposed a holding coil H1 the function of which will presently be explained. The contact springs F1 and F2 are respectively interconnected with the terminal ends thereof over magnetic shunts containing the iron paths M1 and M2 and the air gaps L1 and L2, which shunts, however, do not electronically connect the associated terminals. The principle underlying this structure is explained below.

The flux in the working air gap at the overlap U and the stray fluxes in the air gaps L1 and L2 are utilized so that operative actuation of the contact springs F1 and F2 cannot be effected responsive to excitation of either one of the coils A or C alone. Only the joint excitation of the coils will produce a flux across the working air gap causing the contact springs to be drawn together to effect contact closure. Such operation with joint excitation of the coils is effected because the flux across the working gap becomes obviously additive or cumulative while the stray flux across each of the air gaps L1 and L2 is at least partially cancelled or made ineffective. This will be clear when it is considered that each coil A and C induces its own stray flux across the two air gaps L1 and L2, such fluxes flowing across these air gaps in opposite directions. 7

If there is however excitation only on one side of the overlap, for example, through the coil A and the holding coil H1, the stray fluxes across the air gaps L1 and L2 will be in one direction only; the above-mentioned cancelling or compensating effect will not be present. It is thus possible by suitable dimensioning of the components of the structure to produce with excitation of two coils along one side of the overlap U a condition of balance of the forces across the working air gap and respectively With closed contact, the conditions are however different because the magnetic circuit across the overlap U is directly closed, the flux extending preponderantly across the engaged contact area, and the stray fields across the air gaps L1 and L2 being upon energization of the holding coil considerably weakened.

The difliculties occurring in the plural utilization of the crossing field may be avoided by the provision of special holding windings which are operatively connected after energization of the corresponding line and row windings so as to hold the respectively associated contact element in actuated condition. If the holding windings are used in a coordinate switch according to FIG. 1, they are suitably provided in the form of line and row coils. An example of such an arrangement is indicated in FIG. 4 in which the magnetic shunts are omitted to keep the drawing simple.

The arrangement shown in part in FIG. 4 corresponds in principle to the one shown in FIG. 1 except for the addition of holding coils H1 and H2 which are disposed in parallel either with the line coils or with the row coils; as shown, the holding coils H1 and H2 are disposed in parallel to the column coils C and D. The following is to be observed in connection with such arrangement.

A holding coil must never be disposed along the same side of the overlap of the springs of the corresponding contact elements as the respectively associated line or row coil so as to avoid actuation of a further contact element incident to subsequent energization of another line or row coil crossing the holding coil which happens to be energized to hold a contact element in actuated position. The line or row coil which is to be 1 subsequently energized must extend along the same side example.

It shall be assumed that the contact device 1 has been actuated by energization of the line coil A and the column coil C. The holding coil H1 then assumes the function of maintaining the corresponding contact element actuated. The inlet and outlet belonging to the contact device 1 are in this manner interconnected. When it is now desired to actuate the contact device 4. the row coil B and the column coil D will have to be energized to effect such actuation. The contact or switching element 3 is in such operation likewise excited. However, this excitation is effected only on one side, namely, by means of the holding coil H1 and the line coil B1, both of which are located on the same side of the contact element 3. The energization of the coils 1 B and and H1 remains without efiect on contact element across the air gaps Ll'and L2,in which there is practically no change in the position of the contact springs F1 and F2. The effect of the stray fluxes which is being utilized is particularly pronounced when such fluxes extend approximately in parallel to the direction of motion of the contact springs.

Saturation must however also be considered. A further increase in the electrical excitation cannot become operative once saturation is achieved because it will not produce increased magnetic flux. The entire arrangement is therefore to be dimensioned in view of saturation phenomena so as to operate a coordinate switch comprising such switching devices with a safety factor as high as possible. It would then be possible to provide in an extreme case on one side of the overlap U as high an excitation as desired without etfecting contact closure.

3 due to the shunt conditions explained before.

In FIG. 5, which shows a variant of FIG. 4, the terminals of contact springs belonging respectively to a line or row are interconnected by means of strips St made of magnetically conductive material. These strips may also be utilized for the multiple wiring of the contact spring terminals.

The strips St may be made of permanent magnet material or may in any desired and suitable manner be coated with such material, thus resulting in a structure having polarized contact elements which are in special cases required. The permanent magnet flux may in such a case be utilized to hold an actuated contact element in operated position. The opening of the corresponding contact device would of course require counter excitation of the corresponding line or row coil.

The envelopes of the illustrated contact elements may in the interest of the life of the contacts be filled with a protective gas. It is understood that the term air gap refers in such a case sensibly to the corresponding gas paths.

The coil and contact means cooperating as desired form in effect relay means at the crossing points of the coordinate bank.

Changes may be made within the scope and spirit of the appended claims.

I claim:

1. A switching device for use respectively at a plurality of crossing points of a coordinate switch, each switching device comprising a pair of magnetizable contact springs disposed within a sealed protective tube with the inner ends in overlapping movable relationship inside of said tube forming in normal position thereof a working gap therebetween and the outer ends extending from said tube and being fixedly sealed thereto, column and row control coils embracing at said crossing points the protective tubes of a plurality of said switching devices respectively along each side of the working gap of the contact springs disposed therein, a magnetic shunt between the movable inner end of each spring and the outer fixedly disposed end thereof which extends from said protective tube, each shunt extending along an iron path over a shunt gap which spaces such iron path from the movable inner end of the corresponding spring, and means made of magnetically conductive material for mutually interconnecting corresponding terminals of contact springs of contacts belonging respectively to identical lines or rows.

2. An arrangement according to claim 1, wherein said last-named means is utilized for multiple wiring of said contact terminals.

3. An arrangement according to claim 1, wherein said last-named means is a permanent magnet means.

4. An arrangement according to claim 3, wherein actuated contact springs are held in operated position by the magnetic force of said permanent magnet means.

References Cited in the file of this patent UNITED STATES PATENTS 2,187,115 Ellwood Jan. 16, 1940 2,326,647 Horton Aug. 10, 1943 2,331,514 Stibitz Oct. 12, 1943 2,397,123 Brown Mar. 26, 1946 2,836,676 Wirth May 27, 1958 

